In recent years, hydrogen-dissolved water (also simply called hydrogen water) that dissolves hydrogen gas in (ultra) pure water has been used for washing semiconductor silicon substrates, liquid crystal glass substrates, and the like, and is considered to have a suppressive effect on metal oxidation and spoilage of foods due to its high reductivity. Furthermore, an application of hydrogen-dissolved water to drinking water has been drawing attention because such water may improve various health disorders.
Examples of a process for producing the hydrogen-dissolved water include a process of dissolving, in raw water, hydrogen gas from a gas cylinder or hydrogen gas generated by water electrolysis.
However, when hydrogen gas is simply supplied into raw water at room temperature under atmospheric pressure, the dissolved hydrogen concentration is far below from the saturated hydrogen concentration because nitrogen gas, oxygen gas, and the like dissolved in the raw water interfere with the dissolution of the hydrogen gas.
On this account, for example, there is proposed a process in which a pressure container from which air is removed is filled with hydrogen gas, and raw water is showered in the pressure container to come in contact with the hydrogen gas while keeping the pressure of hydrogen gas at 2 to 10 atmospheres in the pressure container so as to efficiently dissolve the hydrogen gas (Patent Document 1).